This invention relates to an article retention system for transfer equipment in which the article is required to be maintained in a particular orientation for processing, treatment or other operations.
In the manufacture of easy-opening container ends, an end feeding apparatus is provided to feed the ends to each of a series of stations at which the various manufacturing operations are performed on the can ends to produce an easy-opening end. In one can end transferring apparatus manufactured by The Stolle Corporation an apertured indexing belt is used to support the can ends during the forming operations referred to above. Such an apparatus is described in greater detail in U.S. Pat. No. 3,231,065 Kaminski et al and in further detail in U.S. Pat. No. 4,213,324 Kelley et al.
In the manufacture of easy-opening can ends of either the "Ring-pull" or "Push-in" types, it is important that the can ends be maintained in a predetermined orientation throughout the various formation stages of the manufacturing process. Although magnetic means may be used to hold steel can ends in position on the belt, such a system is not suitable for aluminium can ends. Furthermore, magnetic devices are generally inconvenient as they tend to attract magnetic particles and are therefore difficult to maintain.
In an attempt to overcome the above problems, The Stolle Corporation developed a transfer system in which a negative air pressure was applied to a cavity under the indexing belt such that the ends were held in position on the belt by the atmospheric pressure acting on the tops of the ends. Such an arrangement is not entirely suitable for can ends having push-in closures since there is a tendency for the closure tabs to be opened by the negative pressure and the application of the necessary sealing material to the closures is hindered by the vacuum applied to the underside of the can ends. Attempts have been made to modify the above vacuum system to reduce the adverse effects on push-in can ends but such attempts have thus far been only partially successful.